Camber Ratio Research Articles

Aerodynamic performance characteristics of low Re airfoils: A parametric and multi criteria decision study

This research aims at investigating the aerodynamic performance of 51 low Re airfoils and applying a Multi Criteria Decision Making (MCDM) approach for selecting airfoils that align with the specific requirements of small wind turbines (SWTs). The study was carried out by varying the Re from 5 × 104 to 5 × 105; angle of attack (AOA) from −10° to 20°, thickness to chord ratio (0.1–0.9), camber ratio (0.1–0.9), and camber position (10 %–80 %) to evaluate the impact of these parameters on the airfoils’ performance. Furthermore, MCDM approach was applied to identify suitable airfoils optimized for their average lift to drag ratio, stall angle, operating range of AOA, strength, manufacturability, and material cost. The findings showed that of the teste parameters, the AOA and airfoil profile have the most pronounced effects on the airfoil performance. Among the tested airfoils, the E63 provided superior performance at 105 Re with LDR of 76.32, a 37.7 % improvement over that of NACA 4412 which is commonly used for wind turbine blade design. Furthermore, the MCDM results revealed that SG6043, FX63-137, E216 and E62 airfoils were the top-ranked airfoils suitable for SWTs application. These findings can help to produce optimized airfoil designs for increased performance and efficiency of SWTs.

Hydrodynamic Performance Analysis of Camber Ratio Variations on B-series Propeller Types

The hydrodynamic performance of the B-series propeller can be determined by calculating the polynomial equation published by MARIN. Furthermore, analysis and evaluation of B-series propeller modifications can be done by varying the camber ratio of the foil. The camber ratio affects the lift force on the propeller foil, directly affecting the propeller thrust and torque. Numerical calculations were carried out using Computational Fluids Dynamics (CFD), based on Reynolds Averaged Navier Stokes Equations (RANSE) and turbulence model in the form of explicit algebraic stress models (EASM). The overall results of this study show an increase in efficiency of 4.182 on the foil with a camber ratio of 2.2% when compared to the foil camber ratio of 0%.

A Numerical Study of Blade Geometry Effects in a Vertical-Axes Wind Turbines

Several geometrical elements influence the aerodynamic properties of the Darrieus vertical axis wind turbines (VAWTs). Many extant studies have examined properties, such as solidity, pitching axis position (x/c), length of chord (c), blade quantity (N), diameter (d) of the rotor, and aspect ratio. However, not many have examined the shape of the airfoil (AF), which is a vital property that remains to be thoroughly investigated. Therefore, this present study used computational fluid dynamics (CFD) to investigate many airfoils blade characteristics, such as blade thickness (BT), maximum camber ratio (MCR), MCR location (MCRL), and air speed (AS), to determine their impact on VAWT performance. The results demonstrate a blade thickness BT of 10 to 12%, MCR of 0 to 22%, and MCRL of 24 to 23% yield a comparatively high coefficient of power, adequate optimal blade rotation to airspeed ratio (TSR), broader operational area, and high band efficiency while air velocities of 15 to 10% yield a comparatively higher power coefficient.

The aerodynamic performances of the wing-shaped poop sail

ABSTRACT This research proposes a wing-shaped poop which cleverly combines the poop and the wing sail. The wing-shaped poop with the length of 60 m and the height of 16.5 m is designed. The influence of the camber ratios (0.15–0.30) and the thickness ratios (0.10–0.20) on the performance of wing-shaped poop is analyzed. The lift coefficient of the poop increases first and then decreases with the increase of camber ratio and decreases with the increase of thickness ratio. The maximum lift coefficient (2.27) is obtained when the camber ratio is 0.25 and the thickness ratio is 0.1. Considering the influence of the rudder, when the apparent wind angle is 130°, the effective thrust of the poop reaches the maximum of 82 kN. Besides, when the wind comes from the bow, the shape of the poop is changed to reduce wind resistance caused by the wing-shaped poop.

Effect of wingtip flow on hydrodynamic characteristics of cambered otter board

The hydrodynamic characteristics of cambered otter boards with a camber ratio of 15% and aspect ratios of 0.5, 1.0, 1.5, and 2.0 were investigated through flume tank experiments and CFD analysis for the cases in which the wingtips were blocked or unblocked. In the blocked wingtip case, the maximum lift coefficient, stall angle, and lift slope (α: 0° to 15°) were approximately 1.75, 15°, and 0.115 (deg−1), respectively, regardless of the aspect ratio. Comparatively, in the unblocked wingtip case, maximum lift coefficients were 1.74 (stall angle: 40°), 1.65 (35°), 1.54 (25°), and 1.50 (20°), and the lift slope increased from 0.063 to 0.097 (deg−1) as the aspect ratio increased from 0.5 to 2.0. The drag coefficients for all unblocked wingtip models were larger for all considered angles of attack. The effect of the wingtip flow formed around the otter board on the hydrodynamic characteristics was visualized using CFD analysis. A small-scale wingtip plate with a width of 0.1c was designed. Particularly, for boards with aspect ratios of 1.0–1.5 and a 0.1c wingtip plate, lift slopes and maximum lift coefficients approached those for the blocked wingtip cases, and stall angles were close to those for the unblocked wingtip cases.

Hydrodynamic performance of a newly designed biplane-type hyper-lift trawl door for otter trawling

A biplane-type hyper-lift trawl door is newly designed to achieve stable handling while maneuvering, deploying, and stowing with excellent hydrodynamic performances for both bottom and midwater trawling. Flume-tank experiments were carried out to investigate the effect of the aspect ratio (λ, defined as the span b divided by chord c) on the hydrodynamic characteristics of the biplane-type hyper-lift trawl door with a camber ratio of 20% within a wide range of angles of attack (α). The maximum lift coefficients (CLmax) were 2.10 (λ = 1.0, α = 42°), 2.11 (λ = 1.6, α = 37°), and 2.06 (λ = 2.0, α = 28°). With a decreasing stall angle, the maximum lift coefficient remained constant (greater than 2). Considering the compactness and maneuverability of the biplane-type hyper-lift trawl door, an aspect ratio of 2 was adopted for the following experiments. The gap-chord ratio (G/c, G the gap between the fore and rear wings perpendicular to the chord direction) and stagger angle (θ, the included angle between the gap and the line connecting the leading edges of the fore and rear wings) expressing the positional relationship between the fore and rear wings of the biplane-type hyper-lift trawl door were set as 0.75, 0.9, and 1.0 and 20°, 30°, and 40°, respectively, to investigate the hydrodynamic characteristics further. The maximum lift coefficients and stall angles for the five biplane-type models were approximately 2.05 and 30°, respectively. Interestingly, these values were larger than the maximum lift coefficient and stall angle for a monoplane hyper-lift trawl door with the same aspect ratio (= 2) (CLmax = 1.78, α = 22°). This implies that the biplane-type structure contributes to enhancing the lift force and increasing the stall angle. The hydrodynamic forces of the fore and rear wings of the biplane-type hyper-lift trawl door were then calculated using a computational fluid dynamics approach. The lift coefficient for the rear wing was significantly higher than that for the fore wing before an angle of attack of 30° was reached. Nevertheless, the lift force distribution ratio for both the fore wing and the rear wing relative to the entire otter board approached 50%. On the other hand, the stall angle for the rear wing was approximately 30°, and that of the fore wing was around 38°. The fluid between the fore and rear wings tended to flow downstream and to successfully inhibit flow separation on the suction side of the fore wing.

Time domain aero-thermo-elastic instability of two-dimensional non-linear curved panels with the effect of in-plane load considered

This study presents aero-thermo-elastic Instability of two-dimensional Non-linear Curved Panels. Aero-thermo-elasticity plays an important role in the design and optimization of supersonic aircrafts. Furthermore, the transient and nonlinear effects of the thermal and aerodynamic environment encompassing a curved surface cannot be ignored. Accordingly, a homogenous curved plate with a high length-to-width ratio and simply-supported boundary conditions is assumed. The effect of large deflection is included in the equations through von Karman non-linear strain–displacement relations. The thermal load is assumed to be a steady-state temperature non-uniform distribution. Structural properties such as modulus of elasticity and thermal expansion coefficient are assumed to be temperature-dependent. The novelty is incorporating first- and third-order piston theory for the non-linear curved panel flutter analysis under the effects of in-plane and thermal loads. Hamilton’s principle is used and partial differential equations are derived. The semi-analytical weighted residual method for the nonlinear curved panel is utilized. The fourth- and fifth-order Runge–Kutta iterative method are deployed to obtain the non-linear aero-thermo-mechanical deflections. Non-linear frequency analysis of cambered panel with the combined effects of aerodynamics, thermal and in-plane loads is investigated for the first time. The increase in panel curvature leads to a complicated behavior in the non-linear structural frequency variations. With increasing in-plane compressive load, complicated oscillating behavior is observed. More critical instability boundary for cambered panel is detected through the use of third-order piston theory. In addition, with an increase in panel curvature from 0 to 3, the panel displacement increases and for higher camber ratio, it decreases.

A Review on Applications and Effects of Morphing Wing Technology on UAVs

Unmanned aerial vehicles (UAVs) have excelled with their ability to perform the intended task on or without personnel. In recent years, UAVs have been designed for civilian purposes as well as military applications. Morphing wings are changeable wing applications developed as a result of the need for a different lift and drag forces in various phases of the flight of aircraft. It is an application that enables altering the wing aspect ratio, wing airfoil, wing airfoil camber ratio, wing reference area and even different angles of attack are obtained in different parts of the wing. Although morphing wing application has just begun on today’s UAVs, modern airliners already have morphing wingtip devices such as Boeing 777-X’s. The benefits of the use of morphing wings for UAVs make this technology important. UAVs with morphing wing technology; may increase its payload ratio, may achieve a shorter take-off distance, may land and stop in shorter distance, may take-off where runway clearance is limited, has more efficient altitude change at lower engine RPMs, can obtain higher cruise speeds, may decrease its stall speed, may lower its drag if necessary, thus; saving energy and time. This study concludes a review of literature over morphing wing technology.

EFFECTS OF THICKNESS AND CAMBER RATIO ON FLOW CHARACTERISTICS OVER AIRFOILS

This study ensures experimental and numerical investigation of different airfoils to observe and understand how camber ratio affects the flow characteristics over surface of different airfoils. Experimental results in the previous studies were used while the numerical study was performed for present investigation. Reynolds numbers based on the airfoil chords were 1x105 and the angle of attack of 8°. Instantaneous voltage output data were used in order to detect transition location for NACA 4412, oil surface visualization experiments were presented for NACA 2415. In the numerical analysis, values of u/U∞ and turbulent kinetic energy were presented for NACA 4415 airfoil. The experimental results denoted that the change of camber ratio and thickness significantly affected the flow phenomenon such as boundary layer separation or formation and progress of the laminar separation bubble. The long bubble was clearly observed with accumulation of pigments at oil-flow measurement experiment. By increasing the camber ratio with the use of NACA 4412 airfoil, the long bubble turned into the short bubble. Briefly, not only the progress and formation of laminar separation bubble was being affected, but also the onset of transition point was obviously influenced by changing of camber ratio.

Performance of new hyper-lift trawl door for both mid-water and bottom trawling

A hyper-lift trawl door (HLTD) which is not heavily dependent on the bottom for its hydrodynamic performance was developed for both bottom and midwater trawling. Flume tank experiments were conducted on simplified HLTD models with an aspect ratio of 1.0 and camber ratios of 15%, 20%, and 25%. When the distance between the lower wing-end plate of the HLTD and the sea bottom approached 0.01c (where c is chord), the maximum lift coefficient decreased 32–39% compared with that in a free stream sufficiency off bottom. When a steel shoe was installed with a gap of 0.1c between the shoe and the lower wing-end plate, the maximum lift coefficient was greatly improved both in free stream and near the bottom. For HLTDs with camber ratios of 15%, 20%, and 25%, the lift coefficient was 2.14 at the attack angle (α) of 35°, 2.33 (α = 38°), and 2.45 (α = 40°) when in the free stream, and was 2.23 (α = 28°), 2.37 (α = 30°), and 2.46 (α = 32°) when near the bottom. Additionally, towing tank experiments with a 1/10 scale trawl model and four types of otter boards, including vertical V-type, biplane type, rectangular flat type, and the HLTD with a steel shoe, were carried out. It was found that the spread performance of the HLTD was best even though its wing area was only 70% of those of other doors. Furthermore, we compared the performance of the HLTD (with a steel shoe) with that of the vertical V-type door for bottom trawling at sea, and found that the HLTD had superior performance in spreading a trawl. Therefore, the HLTD with a steel shoe was verified as suitable for application in both mid-water and bottom trawling.

Investigation of Differential Evolution Algorithm for a Tandem Cascade Optimization

Due to the fact that there are numerous factors and parameters associated to tandem cascade, and upstream and downstream blades have intensive interference and unknown matching correlation, it is difficult to create tandem blades with high performance based on conventional optimization design method. Therefore, developing an optimization strategy that can take into account key parameters of tandem blades is a feasible way to get optimal design of tandem cascade. In the present work, the Sphere and Rastrigin test functions were adopted to compare and analyze five differential evolution modes, and the DE/r2b/2 evolution mode was then obtained, which can be applied to engineering practice. Based on the present evolutionary pattern, the combination the effects of axial overlap (AO), percent pitch (PP), camber ratio (TR), chord ratio (CR) and approximate incidence angle of the rear blade (Kb-b) are considered comprehensively. Thus, the optimization process and strategy are designed, and the optimization objective function is determined. The optimization results show that under the condition of designed Mach number and large angle of attack (AOA), comparing with the original blades, the optimization makes the static pressure ratio of the tandem blades increased by 1.14%, and the total pressure loss coefficient decreased by 6.57%.

Characterization of Tandem Airfoil Configurations of Axial Compressors

Abstract The objective of the current study is to investigate the effects of geometric parameters on the fluid flow patterns, diffusion factor, load-split, and off-design performance of the tandem configuration under subsonic, rectilinear, cascade flow. A 2-D computational model using finite volume formulation has been developed and validated against available experimental data. The obtained data is presented in a format involving loss parameter and loading and will help the designer to have sufficient number of combinations within the useful range of application. It is observed that general performance behavior of tandem cascade is similar to a single airfoil data. Load shifting from the front airfoil to the rear airfoil is noted at positive axial overlaps and higher camber ratios. An optimum gap ratio of around 2 is observed for the range of configurations investigated. Contrary to the previous literature, the present study indicates higher loading of the front airfoil for the best overall loading-to-loss ratio of the tandem configuration.

Hydroelastic Effects of the Camber Ratio on A Ducted Marine Propeller in A Wake Flow

The effects of the camber ratio on the hydrodynamic and structural behaviors of a NACA-based ducted marine propeller in the wake flow behind an underwater axisymmetric body are numerically studied by computational fluid dynamics methods, in particular, the finite element method. The results are presented in terms of the efficiency, deflection, pressure coefficient, and natural frequencies. It is shown that the wake flow strongly affects the performance of the selected propulsion system. It is shown that the distributions of the camber ratio over the blades of the propeller nonlinearly changes its resistance against cavitation occurrence and deflection, and also changes its hydrodynamic performance and vibrational behavior.

Hydroelastic Effects of the Camber Ratio on a Ducted Marine Propeller in a Wake Flow

Hydroelastic Effects of the Camber Ratio on a Ducted Marine Propeller in a Wake Flow

Numerical investigation of the effects of camber ratio on the hydrodynamic performance of a marine propeller

In this research, effects of the camber ratio distribution over the blades of a NACA marine propeller were numerically investigated on its open water hydrodynamic performance characteristic curves. To investigate this problem, Reynolds averaged Navier-Stokes (RANS) equations were solved using computational fluid dynamics (CFD). Results are presented in terms of vorticity, pressure coefficient, hydrodynamic efficiency, thrust and torque coefficients, and hydrodynamic performance characteristic curves. Results show that the location of the maximum efficiency of the propeller is unchanged versus advance coefficient by changing the camber ratio over the blades. It is shown that magnitudes of the efficiency, torque, thrust, vorticity, pressure coefficient, and the width of the efficiency curve are changed non-linearly by changing the camber ratio.

Numerical investigation on trimming of a single sail in a regatta

In sailing regattas, the actions of sailboats are to meet, overlap, pursue, pass, anti-collide, and defend. The aerodynamic performance of a sail based on a numerical simulation method is reported in this study. The parameters affecting the sail’s aerodynamic force coefficients, namely sailing angle, attack angle, mast shape, pitch angle, and camber ratio, are analyzed. From the results, basic principles and corresponding tactics of sail trimming are discussed and recommended for the start, during the windward, running, and leeward legs, before the finish, and near the marks. Sailors in the regatta should decrease the interaction of air flows around the sail to increase the lift force. The sailing angle, attack angle, pitch angle, and camber ratio should be adjusted to the appropriate degree to speed the boat when it is balanced. Sail trimming tactics have been practiced by professional sailors in regattas during which they can be scientifically supervised to compete against each other at Olympic Games.

Hydrodynamic characteristics of a hyper-lift otter board with wing-end plates

The paper investigates the hydrodynamic characteristics of a hyper-lift trawl door (HLTD), which consists of a cambered plate with two wing-end plates with the leading edge modified into an airfoil shape. Flume experiments were carried out in a circulating water tank using models having a wing area of 625 cm2 and an aspect ratio of 1.0 at camber ratios of 15, 20, and 25 %. To determine the effect of the wing-end plates, models with different size of wing-end plates were tested. Moreover, the effect of heel angle on the hydrodynamic characteristics of the HLTD was also investigated. We concluded that the size of the wing-end plate was significant for h/c = 0.10 (h width of the wing-end plate, c chord length of cambered plate), and the maximum lift coefficients of HLTDs with camber ratios of 15, 20 and 25 % were 2.19, 2.38, and 2.48, respectively, at an attack of angle of 38°. In addition, our findings showed that the effect of the heel angle was very small on the lift, drag and moment coefficients of a HLTD when it slants at heel angles from −20° to 20° during trawling.

Design of trawl otter boards using computational fluid dynamics

Computational fluid dynamics (CFD) analysis was conducted for a biplane-type otter board model to validate the use of CFD analysis in designing otter boards. In the base mode (aspect ratio 3.0, camber ratio 15%, gap-chord ratio 0.91, and stagger angle 30°), CFD analysis results show a maximum lift coefficient value of 1.65 for angle of attack 17.5°, which is in agreement with results of the flume tank experiment (CLmax=1.64 when α=20°) under the same conditions. In addition, the streamline and separation zones around the otter board were visualized and compared to the results from past tank experiment studies. CFD analysis results showed patterns similar to the experimental results, and the details of flow with a trailing vortex were confirmed. We concluded that CFD analysis is useful in the designing and development of otter boards.

A Study of Cross-Sectional Shape of Wing for Underwater Glider at Low Reynolds Number Region

Underwater glider is the glider to use for environmental researches in lake and sea. The Reynolds number of flow around underwater glider is between about 104 ～ 105 and the research for the aerodynamic characteristics of such low Reynolds number region is not so much. So in this study, we investigate the aerodynamic characteristics for various airfoils of under-water glider at low Reynolds number by the towing water tank experiment and 3-dimensional numerical analysis using STAR-CCM+ by IDAJ co. ltd. As results of experiment, the lift-drag ratio of airfoils with camber become larger than those of flat plate. As results of numerical analysis, the effect of maximum camber ratio and maximum camber position and thickness ratio on aerodynamic characteristics and optimum cross-sectional shape of wing for underwater glider are found.

A practical technique for improvement of open water propeller performance

A practical technique for the improvement of open water propeller performance has been described by using a vortex lattice lifting line method together with a lifting surface method. First, the optimum circulation distribution, giving the maximum thrust–torque ratio, has been computed along the radius of the propeller for given thrust and chord lengths, by adopting a vortex lattice solution to the lifting line problem. Then, by using the lifting surface method, the blade sectional properties such as pitch-to-diameter ratio and camber ratio, have been calculated for obtaining the desired circulation distribution. The effects of skew and rake on propeller performance have been ignored. The blades have been discretized by a number of panels extending from hub to tip. The radial distribution of bound circulation can be computed by a set of vortex elements having constant strengths. Discrete trailing free vortex lines are shed at each panel boundary, and their strengths are equal to the differences in strength of the adjacent bound vortices. The vortex system has been built from a set of horseshoe vortex elements, and they consist of a bound vortex segment and two free vortex lines of constant strengths. Each set of horseshoe vortex elements induces an axial and tangential velocity at a specified control point on the blades. An algebraic equation system can be formed by using the influencial coefficients. Once this equation system has been solved for unknown vortex strengths and specified thrust, the optimum circulation distribution and the forces can be computed by using Betz–Lerbs method. When the radial distributions of optimum circulation (loading) and chord lengths have been reached, the lifting surface method can be applied to determine the blade pitch and camber distribution. DTMB 4119 and DTMB 4381 propellers have been adopted for calculations and their hydrodynamic characteristics have been found in their open literature. A very good comparison has been obtained between the results of this practical technique and the experimental measurements.